1. Field of the Invention
This invention relates to a mammogram recording and read-out apparatus comprising a radiation image detector, which is capable of recording a radiation image when it is exposed to radiation carrying image information. This invention particularly relates to a mammogram recording and read-out apparatus for use in operations for recording and reading out the radiation images of the breasts having different sizes.
2. Description of the Related Art
Various radiation image detectors for use in medical fields, and the like, have heretofore been proposed and used in practice. The radiation image detectors are capable of recording a radiation image of an object when being exposed to radiation carrying image information of the object and are capable of outputting an electric signal in accordance with the recorded radiation image.
Examples of the radiation image detectors include radiation image detectors utilizing semiconductor materials, which form electric charges when being exposed to the radiation. As the radiation image detectors utilizing the semiconductor materials, optical read-out types of radiation image detectors and TFT read-out types of radiation image detectors have heretofore been proposed.
As the optical read-out types of the radiation image detectors, there have been proposed the radiation image detectors comprising a first electrode layer, which has transmissivity to the radiation, a recording photo-conductor layer, which forms electric charges when it is exposed to the radiation having passed through the first electrode layer, a charge transporting layer, which acts as an insulator with respect to latent image charges and which acts as a conductor with respect to transported charges having a polarity opposite to the polarity of the latent image charges, a reading photo-conductor layer, which forms electric charges when it is exposed to reading light, and a second electrode layer constituted of a plurality of linear electrodes, which have transmissivity to the reading light and are arrayed in parallel. The first electrode layer, the recording photo-conductor layer, the charge transporting layer, the reading photo-conductor layer, and the second electrode layer are overlaid in this order.
As the TFT read-out types of the radiation image detectors, there have been proposed the radiation image detectors comprising an electrode layer, which has transmissivity to the radiation, a photo-conductor layer, which forms electric charges when it is exposed to the radiation having passed through the electrode layer, and an electric signal detecting layer, which is constituted of a plurality of detecting devices arrayed in a two-dimensional pattern. Each of the detecting devices is provided with a capacitor, which accumulates the electric charges having been formed in the photo-conductor layer, and a TFT switch for the reading of the electric charges from the capacitor. The electrode layer, the photo-conductor layer, and the electric signal detecting layer are overlaid in this order.
Also, various mammogram recording and read-out apparatuses for performing operations for recording and reading out X-ray images of the breasts have heretofore been proposed. (A mammogram recording and read-out apparatus is proposed in, for example, Japanese Unexamined Patent Publication No. 5(1993)-173266.) Further, mammogram recording and read-out apparatuses utilizing the radiation image detectors described above have been proposed.
In cases where the operations for recording and reading out the X-ray images of the breasts are performed by use of the mammogram recording and read-out apparatuses described above, since the sizes of the breasts vary for different persons to be examined, the problems described below occur. Specifically, for example, in cases where the size of the radiation image detector is smaller than the size of the breast, it is necessary for the image recording and read-out operations to be performed a plurality of times for different regions of the breast. In such cases, the dose delivered to the person to be examined is not capable of being kept small. Conversely, in cases where the size of the radiation image detector is larger than the size of the breast, for example, when the breast is sandwiched and compressed between a compression plate and the radiation image detector for the image recording and read-out operation, the problems occur in that, besides the breast, the abdomen is sandwiched between the compression plate and the radiation image detector, and the breast is not capable of being compressed sufficiently. Also, psychological burden given to the person to be examined is not capable of being kept light. Therefore, in the cases of the operations for recording and reading out the X-ray images of the breasts, it is necessary for the image recording and read-out operations to be performed by use of the radiation image detectors having the sizes in accordance with the sizes of the breasts.
However, the cost of the aforesaid radiation image detectors utilizing the semiconductor materials is high. Therefore, in cases where the radiation image detectors matched with the sizes of the breasts of the persons to be examined are prepared, the cost of the image recording and read-out apparatus is not capable of being kept low.